01 - Preheat the oven to 375°F. Grease a standard donut pan with butter or non-stick spray and set aside.
02 - In a large mixing bowl, whisk together the all-purpose flour, granulated sugar, baking powder, and salt until evenly distributed.
03 - In a separate bowl, whisk together the milk, eggs, melted butter, and vanilla extract until smooth and well combined.
04 - Pour the wet mixture into the dry ingredients and fold gently with a spatula until just combined. Avoid overmixing to keep the donuts tender.
05 - Transfer the batter to the donut pan, filling each cavity approximately two-thirds full. Smooth the tops if needed.
06 - Bake for 13 to 15 minutes, or until a toothpick inserted into the center of a donut comes out clean. Let cool in the pan for 5 minutes, then transfer to a wire cooling rack to cool completely.
07 - Using a hand mixer or stand mixer, beat the softened butter on medium speed until light and creamy. Gradually add the powdered sugar, beating well after each addition, until the mixture is fluffy and pale.
08 - Add the strawberry puree, vanilla extract, salt, and pink food coloring if using. Beat on medium-high speed until the frosting is smooth, spreadable, and uniformly colored.
09 - Once the donuts are completely cool, spread or pipe the strawberry buttercream frosting generously over the tops. Serve immediately or store in an airtight container.